In recent years the need for alternative sources of electrical energy has grown significantly as a result of increased and uncertainty in oil prices, growing environmental concerns, and the lack of sufficient alternative energy supplies. Accordingly, wind generator systems have gained support as an alternate energy source. Wind generators have been shown to provide a safe and clean source of electric power. Systems, such as large or big wind generators, have been developed having large blades (often more that 18 feet in length) mounted on high towers that can produce more than 35 kilowatts (kW) of power with wind speeds of 20 knots. Such systems are typically used in combination with other wind generators, such as along coastal areas for providing electrical power directly to power grids. Such systems have also been used in rural areas, such as farms, for providing supplemental power or reducing electrical costs.
Small wind generators mounted on smaller towers have also been developed for use such as for residential application and have been used as remote or distributed power sources. Such systems are often connected to the main electric service to the home thereby allowing sufficient powering of the home and for sending excess power generated by the wind generator back to the power grid. Typically, theses small wind generators rotate at speeds that vary with wind speed and have a plurality of blades that drive a rotor coupled to a gearbox that operates to increase the rotation speed of a generator for producing electric power.
In order to reduce maintenance and increase efficiency, systems have been developed having relatively large synchronous ring generators that permit the rotor to be directly coupled to the generator without the need of a gearbox. Unfortunately, while such systems have reduced maintenance costs and have increased the efficiency of the systems, wind generator systems continue to suffer from relatively significant maintenance costs. Further, forces being exerted to the systems due to wind increase in proportion to the cube of wind speed. Accordingly, high wind speeds often encountered by small wind generator systems, even if only occasional or momentary, can damage system components. This is particularly true for wind generators having relatively large blades such as typically required for small wind generators that depend on the relatively large blades to harvest lower-energy winds. Thus, small wind generator systems are typically designed having means for preventing system damage due to such high speed winds. Such means include blade pitching, airfoil spoilers, blade tip breaks, and the like. Means such as braking means or means that act upon the entire blade apparatus rather than on individual blades have also been developed. Unfortunately, all such means significantly add to the complexity and expense of the wind generator systems and significantly add to their maintenance down time and costs. In addition, systems having such means typically require routine maintenance which significantly increases their operating costs. This is particularly true when parts or components must be repaired or replaced which often requires significant rebuild or major dismantling of the system to replace a component. Further, during operation, such means often result in significant power drops or the cessation of power generation during such high wind conditions.
Another problem associated with small wind generators is that they are often acoustically noisy and are undesirable for many residential applications. Further, small or low wind generator systems for mounting to building structures are generally not aesthetically pleasing, often require extensive building modifications, and are prohibited under many building codes.
Accordingly, due to the complexity of many wind generators used in small wind or distributed power the need for a simple modular and easy to maintain generator is significant in not just reducing cost to the consumer but in the cost of manufacture and maintenance.
Consequently, a need exists for a small wind generating system that has reduced cyclic cost, increased reliability and improved maintenance needs and costs, that is acoustically and aesthetically acceptable for residential operation, and which is relatively inexpensive to manufacture and install.